Lid and door for a vacuum chamber and pretreatment therefor

ABSTRACT

Replaceable parts for a vacuum chamber including an aluminum lid and a quartz door and shield, are treated to clean and roughen their surfaces to increase adhesion of materials deposited thereon during substrate processing in said chamber, thereby reducing downtime of the equipment. The parts can be chemically cleaned, rinsed to remove the chemicals and dried in a first step; subjected to bead blasting to roughen the surface of the part and improve adhesion thereon of deposited material; in a succeeding step the part be cleaned ultrasonically to remove all loose particles; and in a last step the parts rinsed and dried to remove moisture, prior to packaging or using the part. A novel single-piece machined aluminum lid has an extension wall from a first surface that fits into the door of the chamber, and an overlying portion of said first surface that sealingly engages the door when the lid is closed.

This is a continuation of application Ser. No. 08/335,611 filed Nov. 8,1994, now U.S. Pat. No. 5,565,058 which is a division of Ser. No.07/936,433 filed Aug. 27, 1992, now U.S. Pat. No. 5,401,319 issued Mar.28, 1995.

This invention relates to improved replaceable parts for a vacuumchamber. More particularly, this invention relates to replaceable partsfor a vacuum etch chamber that are pre-treated to extend the time forreplacement.

BACKGROUND OF THE INVENTION

Vacuum chambers are well known and are employed in the semiconductorindustry to etch and deposit thin films and form contacts insemiconductor substrates during manufacture of, inter alia, integratedcircuits. State-of-the art processing chambers form a part of a systemable to condition and preclean substrates for vacuum processing andprocess them without leaving a vacuum environment.

However, a substrate preclean step, while it is effective in removingmaterial adhered to the surface of the substrate, distributes thismaterial on other surfaces within the vacuum chamber, e.g., on the wallsor shields, lid and door of the chamber. In time there is a build up ofthis material that causes flakes to form on these surfaces that candeposit onto the substrate surface. At that point the chamber must bedisassembled for cleaning.

The present lid for a vacuum etch chamber comprises a two-piece aluminumlid separated by an RF gasket, which is a low resistance contact for the60 MHz RF power supply for the vacuum chamber. Two aluminum plates arescrewed together by a plurality of screws that fasten the two platestogether so they make good contact to the RF gasket therebetween. Asmaterial builds up on the lid however, as described hereinabove, it mustbe periodically cleaned to remove the built up material. This isgenerally done by a wet chemical cleaning process which requires thatthe lid be disassembled, the screws removed, the lid cleaned and thenthe lid be re-assembled. However, the act of assembly, e.g., insertingand fastening the screws, itself creates particles, so that the chamberis not clean, i.e., free of particles, even after the cleaning step.Other parts of the vacuum chamber, such as the door for the lid and ashield around the substrate support that prevents material fromdepositing on the walls of the chamber, must also be periodicallycleaned; this adds to the downtime of the equipment and consequentlyincreases costs of manufacture.

Thus it would be desirable to have a vacuum chamber lid that does nothave to be disassembled and assembled again for cleaning; further itwould be desirable to pre-treat replaceable parts for a vacuum chamberso that particles generated in the vacuum chamber that adhere to thelid, door and shield surfaces have improved adherence to these surfaceswith the result that the time between cleaning cycles can be extended,thereby reducing downtime of the equipment.

SUMMARY OF THE INVENTION

The present invention provides a novel lid and door for a vacuum chambercomprising a single, machined aluminum plate that sealingly engages aquartz ring or door, and, when the lid and door to the vacuum chamberare closed, in turn fits inside a shield surrounding the substratesupport. The lid, shield and door replaceable parts are pre-treated sothat particles generated within the chamber during precleaning of thesubstrate and processing thereof will better adhere to these surfaces,allowing more substrates to be processed before the vacuum chamber needsto be taken apart and cleaned or parts replaced. This pre-treatmentcomprises a bead blasting step that creates an irregular surface in thealuminum and quartz materials of the replaceable parts, e.g., lid, doorand shield respectively, to which materials or particles generated inthe chamber adhere better than on a smooth surface, followed by removalof all particles remaining on the surface after the bead blasting stepby an ultrasonic cleaning step of the replaceable parts. Thispre-treatment produces aluminum and quartz door/lid/shield combinationsthat have a long lifetime in a vacuum processing chamber.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross sectional view of a replaceable lid, door and shieldfor a vacuum processing chamber.

FIG. 2 is a flow chart for the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates the novel one piece aluminum lid of the invention, aquartz door therefor and a quartz substrate support shield for a vacuumprocessing chamber. The lid is opposed to the cathode within the chamberon which the substrate to be treated is placed during processing. Thelid and door of the invention have been pre-treated in accordance withthe process of the invention.

The extension wall 14 fits inside a quartz door 16. When the lid 14 isin place and the door 16 is closed, the door 16 fits atop a quartzshield 18 which is shaped to surround the cathode 17 onto which thesubstrate to be processed is located during processing. The door 16 israised and lowered with lid 12 stationary by an externally drivenactuator. At the same time the door 16 is raised and lowered, ceramicfingers (not shown), which pass through slots in the quartz shield 18,raise and lower the substrate onto the cathode 17. This occurs duringthe transfer of substrates into and out of the chamber. The fixed quartzshield 18 serves to prevent material etched from the substrate fromadhering to the walls of the vacuum chamber (not shown). The lid 12 alsohas an overlying portion 20 of said first surface that contacts andseals the door during processing. A suitable O-ring seal (not shown)conventionally is used to seal the chamber when a vacuum is drawn.

The aluminum lid 12 and the quartz door 16 and shield 18 are pre-treatedin accordance with the cleaning process of the invention, described ingreater detail hereinbelow.

The novel lid of the invention requires no screws, thereby generatingfewer particles in a vacuum preclean or processing chamber; has apre-treated surface to which particles generated during processingbetter adhere; does not require an RF gasket, resulting in bettergrounding of the lid; and no assembly or disassembly of the lid isrequired for cleaning or replacement. A simple replacement of the lidand the door can be effected when required, reducing the downtime of theequipment. The lid, door and shield also can be readily re-cleaned andre-treated for reuse in any suitable vacuum chamber. Aluminum parts andquartz parts are recycle-cleaned by a combination of bead blasting andchemical cleaning steps. The last step in both cases is a bead blastingstep followed by ultrasonic processing in deionized water, rinsing anddrying as explained further hereinbelow.

The pretreatment process of the invention comprises a bead blasting stepfollowed by an ultrasonic cleaning step.

The bead blasting step treatment of the aluminum lid and the quartz dooris suitably effected by bombarding the lid, the door and the shieldusing about 80 psi of pressure and aluminum oxide powder having a rathercoarse grit, suitably about 36-80 grit in size. Bead blasting can becarried out in commercially available bead blasting equipment. The beadblasting powder particles must be large enough to make the aluminumsurface of the lid and the quartz door and shield surfaces slightlyirregular or roughened. The machined one-piece aluminum lid canwithstand bead blasting with coarser grit size material because it isthicker than the prior art two-plate aluminum sheet metal lid, and thusit is more durable. The irregular surfaces, on a microscopic scale, willenhance interface crack propagation of material that may be depositedduring substrate processing. The surface irregularities will result inthe breaking up of the deposited films into sections that are small withrespect to flake sizes, which significantly hinders flaking. Inaddition, the irregular or roughened surfaces have an increased surfacearea to which material can deposit, increasing the amount of depositedmaterial that can be accommodated.

The bead blasting step is followed by an ultrasonic cleaning step thatremoves all loose particles on the surfaces of the lid, door and shield,whether they are due to particles remaining from the bead blasting, orminute particles of aluminum, quartz, dust particles and the like. Thelid, door and shield are first rinsed with deionized water and immersedin an ultrasonic cleaner filled with deionized water. Suitableultrasonic cleaners are commercially available and are generally set torun at power densities of from about 35-70 Watts/gallon using a chambercontaining about 10 gallons of deionized water for several minutes. Assoon as the ultrasonic generator is turned on, a cloud of formerlyembedded solid residue is seen to form over the bead blasted surfacesfrom which it originated. This cloud quickly dissipates and the solidmaterial removed either remains in aqueous suspension or settles out.Thus, most of the activity of ultrasonic processing occurs during theinitial few seconds of treatment. Treatment is usually continued forabout 5 minutes however, in order to assure thorough removal of allloose solid material. The parts are then thoroughly rinsed with hotdeionized water to ensure that no particles remain on the surfaces ofthe treated aluminum and quartz parts.

Lastly, the aluminum lid and quartz door and shield parts are dried toremove all moisture from their surfaces. Suitably the parts can be blowndry with filtered air or nitrogen and then lightly baked, e.g., at about60° C. for one-half hour in filtered air atmosphere to remove allmoisture from the parts. The cleaned parts can then be packed forshipment.

In a preferred cleaning process, prior to the bead blasting step theparts are chemically cleaned to remove surface contamination, such asoxides from the aluminum and organics from the quartz surfaces. Asuitable chemical cleaning solution for ceramics for example can be 1/3nitric acid, 1/3 hydrofluoric acid and 1/3 water. Dipping the part inthe chemical cleaning solution for about 15 seconds is generallysufficient. The part is then rinsed with deionized water to remove thechemicals and blown dry using clean, filtered air or nitrogen.

FIG. 2 is a flow chart of the preferred embodiment of the process of theinvention, showing the chemical clean first step, followed by a beadblasting step, an ultrasonic cleaning step, and lastly the part finishedby rinsing and drying and packaging the part.

Treating the lid and quartz parts of the vacuum chamber in accordancewith the process of the invention, and utilizing the simplified,sturdier lid of the present invention, results in a cleaner vacuumchamber, one that can process more substrates than prior art chamber,reducing downtime of the equipment, and also provides a fast and lowcost method of cleaning the chambers, and replacing the above-describedparts.

Although the above invention has been described in terms of certainpresently preferred embodiments, one skilled in the art will know ofalternative embodiments of processing and equipment which are meant tobe included herein. For example, although semiconductor substrates aregenerally silicon wafers which are circular in cross section, resultingin shields and cathode supports that are also circular in cross section,other substrates such as rectangular glass plates can also be employed.Other materials can be substituted for aluminum, such as stainlesssteel; and other cleaning and rinsing steps inserted into the processfor particular results. The invention is only meant to be limited by theappended claims.

We claim:
 1. A single-piece machined aluminum lid for a vacuum chamberhaving a vertically movable door in a sidewall thereof, said lid havinga single perpendicular extension wall extending downwardly from said lidand a first surface that overlies and sealingly engages said door whenthe lid is closed so that the lid extension wall is inside of said door,wherein said lid is treated by bead blasting said first surface toroughen it, then ultrasonically cleaning it to remove surface particlesand then rinsing and drying the lid.